Method for fabricating a flux concentrating system for use in a magnetoelectronics device

ABSTRACT

A method for fabricating a flux concentrating system ( 62 ) for use in a magnetoelectronics device is provided. The method comprises the steps of providing a bit line ( 10 ) formed in a substrate ( 12 ) and forming a first material layer ( 24 ) overlying the bit line ( 10 ) and the substrate ( 12 ). Etching is performed to form a trench ( 58 ) in the first material layer ( 24 ) and a cladding layer ( 56 ) is deposited in the trench ( 52 ). A buffer material layer ( 58 ) is formed overlying the cladding layer ( 56 ) and a portion of the buffer material layer ( 58 ) and a portion of the cladding layer ( 56 ) is removed.

FIELD OF INVENTION

The present invention relates generally to magnetoelectronics devices,and more particularly to a method for fabricating a flux concentratingsystem for use in magnetoelectronics devices.

BACKGROUND OF THE INVENTION

Magnetoelectronics devices, spin electronics devices and spintronicsdevices are synonymous terms for devices that use the effectspredominantly caused by electron spin. Magnetoelectronics effects areused in numerous information devices, and provide non-volatile,reliable, radiation resistant, and high-density data storage andretrieval. The numerous magnetoelectronics information devices include,but are not limited to, magnetic random access memory (MRAM), magneticsensors and read/write heads for disk drives.

Generally, a magnetoelectronics information device is constructed withan array of magnetoelectronics elements (e.g., giant magnetoresistance(GMR) elements or magnetic tunnel junction (MTJ) elements) formed in asubstrate that may also include a variety of semiconductor devices, suchas, for example, MOSFETs. The magnetoelectronics elements are programmedby the magnetic field created from a current-carrying conductor.Typically, two current-carrying conductors, one formed underneath themagnetoelectronics element (the digit line) and one formed overlying themagnetoelectronics element (the bit line), are arranged in cross pointmatrix to provide magnetic fields for programming of themagnetoelectronics element.

Advanced semiconductor processes often use metal interconnects for thecurrent-carrying conductors. One method of forming the bit line metalinterconnect is by a damascene or inlaid process during which a trenchis patterned and etched in a dielectric layer, followed by thedeposition of a metal layer within the trench. Flux concentratingsystems often are formed proximate to the metal interconnect. Fluxconcentrating systems typically utilize top cladding layers formedoverlying the metal interconnect to concentrate the magnetic flux of theinterconnect toward the magnetoelectronics element. Such systems alsotypically utilize cladding layers formed on the sides of the metalinterconnect to focus the magnetic flux to the underlyingmagnetoelectronics element. Without cladding layers, high currents arerequired to achieve the desired magnetic field strength. These highcurrents may adversely affect nearby magnetoelectronics elements notbeing programmed.

However, prior art methods to provide top cladding layers overlying bitlines have proved unsatisfactory. Such methods often result in roughnessof the metal layer of the bit line, which may adversely affect thecoercivity of the top cladding layer. Other methods may result in a“magnetic gap” between the cladding layer and the metal layer of the bitline, that is, the distance between the cladding layer and the metallayer of the bit line is sufficiently large that performance of thecladding layer is compromised. Still other methods may result innon-planar top cladding layers that exhibit detrimental magneticinteraction with pre-existing side cladding layers.

Accordingly, it is desirable to provide an improved method forfabricating a flux concentrating system for use in a magnetoelectronicsdevice. Other desirable features and characteristics of the presentinvention will become apparent from the subsequent description and theappended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments andtherefore do not limit the scope of the invention, but are presented toassist in providing a proper understanding. The drawings are not toscale and are intended for use in conjunction with the explanations inthe following detailed description. The present invention willhereinafter be described in conjunction with the appended drawings,wherein like reference numerals denote like elements, and:

FIGS. 1-5 illustrate schematically, in cross-section, a method forfabricating a flux concentrating system in accordance with an exemplaryembodiment of the invention;

FIGS. 6-10 illustrate schematically, in cross-section, a method forfabricating a flux concentrating system in accordance with anotherexemplary embodiment of the invention;

FIGS. 11-15 illustrate schematically, in cross-section, a method forfabricating a flux concentrating system in accordance with a furtherexemplary embodiment of the invention;

FIG. 16 is an enlarged perspective view of a portion of a random accessmemory device formed in accordance with an exemplary embodiment of thepresent invention; and

FIG. 17 illustrates schematically, in cross-section, a method forfabricating a flux concentrating system in accordance with yet anotherexemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following detailed description is of exemplary embodiments only andis not intended to limit the invention or the application and uses ofthe invention. Rather, the following description provides a convenientillustration for implementing exemplary embodiments of the invention.Various changes to the described embodiments may be made in the functionand arrangement of the elements described without departing from thescope of the invention as set forth in the appended claims. Furthermore,there is no intention to be bound by any theory presented in thepreceding background of any exemplary embodiments of the invention.

Turning now to the figures, FIGS. 1-5 illustrate a method in accordancewith one exemplary embodiment of the present invention for fabricating aflux concentrating system for use in a magnetoelectronics device.Referring to FIG. 1, the method may begin by providing a bit line 10,which is defined as a current-carrying conductor that is formedoverlying one or more magnetoelectronic elements such that at least oneof the magnetoelectronic elements is magnetically coupled to bit line10. Bit line 10 is formed within an insulative material substrate 12,which may be any suitable insulative material such as a dielectricmaterial formed from silicon oxide (SiO₂), tetraethyl orthosilicate(TEOS), silicon nitride (SiN) or other low temperature material. As usedherein, “low temperature material” means any material that is formed attemperatures no higher than about 250° C. Temperatures higher than thismay adversely affect the magnetic properties of the materials thatcomprise bit line 10. Substrate 12 may include one or moremagnetoelectronics elements or may overly another substrate thatincludes one or more magnetoelectronics elements that are magneticallycoupled to bit line 10.

Bit line 10 may be formed within insulative material substrate 12 by anysuitable damascene process as is well known in the semiconductorindustry. In one exemplary embodiment of the invention, bit line 10 maycomprise a conducting line 22 formed of copper (Cu), aluminum (Al), gold(Au), silver (Ag) or the like, or a combined alloy thereof. Preferably,conducting line 22 is formed of copper.

In another exemplary embodiment of the invention, bit line 10 furthercomprises cladding layer 20 that is positioned adjacent a first surface4 and a second surface 6, such as the sides, of conducting line 22 sothat the magnetic flux from conducting line 22 may be focused to anunderlying magnetoelectronics element. Cladding layer 20 may be formedusing conventional methods as are well known in the semiconductorindustry. In one embodiment of the invention, cladding layer 20comprises a flux concentrating layer 16. Flux concentrating layer 16 maycomprise any suitable material that has the characteristic ofconcentrating magnetic flux produced by the current flowing inconducting line 22. Flux concentrating layer 16 is an electricallyconducting magnetic material having high permeability, such as nickeliron of any suitable proportion of nickel and iron (NiFe), or anysuitable material having sufficiently high permeability to concentratethe magnetic flux in the desired area and be metallurgically compatiblewith the material structure. Flux concentrating layer 16 extends alongsurfaces 4, 6 of conducting line 22. In another embodiment of theinvention, cladding layer 20 may comprise a first barrier layer 14. In apreferred embodiment, first barrier layer 14 extends along sides 4, 6and also along a bottom surface 8 of conducting line 22 to prevent orreduce diffusion of the metal that forms conducting line 22 intosubstrate 12. First barrier layer 14 may comprise cobalt (Co), cobaltiron (CoFe), tantalum (Ta), tantalum nitride (TaN) or other suitablematerial. In a further embodiment of the invention, cladding layer 20may comprise second barrier layer 18, which is positioned adjacentsurfaces 4, 6, 8 of conducting line 22 and serves as a barrier betweenconducting line 22 and flux concentrating layer 16. Second barrier layer18 may be formed of Ta, TaN, tantalum silicon nitride (TaSiN) or othersimilar material.

Referring to FIG. 2, a first material layer 24 is formed overlying bitline 10 and substrate 12 and a second material layer 26 is formedoverlying first material layer 24. First material layer 24 and secondmaterial layer 26 may be selected such that first material layer 24serves as an etch stop when second material layer 26 is subjected tostandard etching techniques. For example, first material layer 24 may beformed of a material that is selective to a particular etch chemistry,or first material layer 24 may be formed of a material that provides anendpoint signal for stopping or slowing the etch process. Examples oflow temperature materials suitable for forming first material layer 24include, but are not limited to, plasma-enhanced nitride (PEN), TEOS,silicon nitride (SiN), aluminum nitride (AlN), silicon carbide (SiC),silicon carbon nitride (SiCN), silicon carbon oxyhydride (SiCOH),silicon oxynitride (SiON) and the like. Second material layer 26 alsomay be formed of these materials as long as first material layer 24 isformed of a material different from second material layer 26 and as longfirst material layer 24 serves as an etch stop relative to secondmaterial layer 26. In a preferred embodiment of the invention, firstmaterial layer 24 is formed from low temperature plasma-enhanced nitrideand second material layer 26 is formed from TEOS.

Referring to FIG. 3, a portion of second material layer 26 may beremoved by patterning and etching using conventional techniques to forma trench 28 within second material layer 26. It will be appreciated thattrench 28 should be at least as wide as bit line 10 to focus themagnetic flux of bit line 10 to an underlying magnetoelectronics element(not shown). Second material layer 26 may be etched utilizing anystandard etching technique but is preferably etched by a dry etch inplasma. Second material layer 26 may be etched such that etching isstopped by first material layer 24, which as previously described isformed as either a layer of material that is not amenable to the etchingprocess used to etch second material layer 26, or which indicates achange of material that stops the etching due to an endpoint detectionsignal.

Next, as illustrated in FIG. 3, a cladding layer 30 may be formed withintrench 28. Cladding layer 30 may be formed using any suitable depositionprocess such as plasma vapor deposition (PVD), ion beam deposition(IBD), atomic layer deposition (ALD), electroplating or electrolessplating. Cladding layer 30 may be formed of the same materials that formcladding layer 20 or may be formed of different materials. In oneexemplary embodiment of the invention, cladding layer 30 comprises aflux concentrating layer 34. Flux concentrating layer 34 has thecharacteristic of directing magnetic flux produced by the currentflowing in conducting line 22 toward a magnetoelectronics elementpositioned below bit line 10. Similar to flux concentrating layer 16,flux concentrating layer 34 should be an electrically conductingmagnetic material having high permeability, such as nickel iron (NiFe),or any suitable material having sufficiently high permeability toconcentrate the magnetic flux in the desired area and be metallurgicallycompatible with the material structure. In another exemplary embodimentof the invention, cladding layer 30 may also comprise a first barrierlayer 32 formed underlying flux concentrating layer 34 and contactingthe surfaces of trench 28, that is, overlying first and second materiallayers 24, 26. First barrier layer 32 acts as a diffusion barrierbetween the material of flux concentrating layer 16 and conducting line22. First barrier layer 32 may comprise cobalt (Co), cobalt iron (CoFe),tantalum (Ta), tantalum nitride (TaN) or other suitable material. In afurther exemplary embodiment of the invention, cladding layer 30 mayalso comprise a second barrier layer 36 that is deposited overlying fluxconcentrating layer 34. Second barrier layer 34 prevents or reducesdiffusion of the material of flux concentrating layer 16. Second barrierlayer 34 may be formed of Ta, TaN, TaSN or other similar material.

Referring to FIG. 4, a buffer material layer 38 then may be formedoverlying cladding layer 30. Buffer material layer 38 may be formed ofany suitable low temperature material such as PEN, TEOS, SiO₂, SiN, AlN,SiC, SiCN, SiCOH, SiON and the like. In a preferred embodiment of theinvention, buffer material layer 38 is formed from TEOS.

As illustrated in FIG. 5, any excess portion of cladding layer 30, suchas cladding layer material formed overlying a top surface of secondmaterial layer 26, and any excess buffer material layer 38 then may beremoved by any suitable planarization process known in the semiconductorindustry, such as, for example, chemical mechanical planarization orelectrochemical mechanical planarization, or any other suitable removalprocess, such as etching. Once a suitable portion of cladding layer 30and buffer material layer 38 has been removed, a portion of claddinglayer 30 remains to form a top cladding layer 40 over bit line 10.Depending on the amount of planarization performed, the top claddinglayer 40 may or may not be substantially planar. Accordingly, as will beappreciated, a flux concentrating system 42 comprising top claddinglayer 40 overlying first material layer 24 may be formed using theabove-described exemplary embodiment of the present invention. Inaddition, flux concentrating system 42 may also comprise cladding layers20 of bit line 10.

FIGS. 6-10 illustrate another exemplary embodiment of the presentinvention. Elements of FIGS. 6-10 that have the same reference numbersas FIGS. 1-5 are the same corresponding FIGS. 1-5 elements. The methodmay begin by providing bit line 10 that is formed within insulativematerial substrate 12. First material layer 24 is formed overlying bitline 10 and substrate 12 and a second material layer 50 is formedoverlying first material layer 24. First material layer 24 and secondmaterial layer 50 may be selected such that first material layer 24serves as an etch stop when second material layer 50 is subjected to dryplasma etching. For example, first material layer 24 may be formed of amaterial that is selective to dry plasma etching, or first materiallayer 24 may be formed of a material that provides an endpoint signalfor stopping or slowing the etch process. In addition, first materiallayer 24 and second material layer 50 preferably are selected such that,when subjected to a particular wet etch process, the wet etch chemistryetches first material layer 24 significantly faster than second materiallayer 50. As used herein, to etch “significantly faster” means to etchat least about twice as fast. Thus, the wet etch chemistry etches firstmaterial layer 24 at least about twice as fast as second material layer50. In a preferred embodiment of the invention, the wet etch chemistryetches first material layer 24 about ten times as fast as secondmaterial layer 50. Examples of low temperature materials suitable forforming first material layer 24 include, but are not limited to,plasma-enhanced nitride (PEN), TEOS, silicon nitride (SiN), aluminumnitride (AlN), silicon carbide (SiC), silicon carbon nitride (SiCN),silicon carbon oxyhydride (SiCOH), silicon oxynitride (SiON) and thelike. Second material layer 50 also may be formed of these materials aslong as first material layer 24 serves as an etch stop relative tosecond material layer 50 in dry plasma and as long as a wet etch offirst material layer 24 is significantly faster than second materiallayer 50. In another preferred embodiment of the invention, firstmaterial layer 24 is formed from low temperature PEN and second materiallayer 50 is formed from TEOS.

Referring to FIG. 7, a portion of second material layer 50 and firstmaterial layer 24 may be removed by patterning and etching usingconventional techniques to form a trench 52 within second material layer50 and first material layer 24. It will be appreciated that trench 50should be at least as wide as bit line 10 so that the subsequentlydeposited cladding layer, as described in detail below, may focus themagnetic flux of bit line 10 to an underlying magnetoelectronics element(not shown). Second material layer 50 is preferably etched by a dry etchin plasma, as is well known in the semiconductor industry. In oneexemplary embodiment of the invention, second material layer 50 may beetched such that etching is stopped by first material layer 24, which aspreviously described is formed as either a layer of material that is notamenable to the dry etching process, or which indicates a change ofmaterial that stops the etching due to an endpoint detection signal. Inanother embodiment of the invention, an etch of second material layer 50is performed, followed by a subsequent overetch of first material layer24, which overetch does not result in exposure of bit line 10. Firstmaterial layer 24 then is etched with a wet etch chemistry that etchesfirst material layer 24 significantly faster than second material layer50. First material layer 24 is etched until bit line 10 is exposed oruntil at least a substantial amount of first material layer 24 isremoved. In an optional embodiment, to ensure adequate removal of firstmaterial layer 24 from bit line 10, first material layer 24 may beoveretched until trench 52 includes an undercut 54 of first materiallayer 24. Any suitable amount of overetch may be performed to ensureadequate removal of first material layer 24. The percentage of overetchis defined as the percentage of the time it takes to etch the thicknessof first material layer 24. For example, if it takes “x” seconds to etcha layer of first material layer 24 having a thickness “y”, a 100%overetch is an overetch of another x seconds or an entire etch time of2× seconds. Similarly, a 50% overetch is an overetch of another 0.5×seconds or an entire etch time of 1.5× seconds. In one exemplaryembodiment, the overetching may be about 100%. In a more preferredembodiment of the invention, the overetching may be from about 0% toabout 50%.

In another exemplary embodiment of the invention, a pre-depositionsputter etch of trench 52 may be performed to remove native oxide from asurface 64 of bit line 10 and to smooth surface 64 of bit line 10. Thepre-deposition sputter etch may be performed using any conventionaltechnique known in the semiconductor industry.

Referring to FIG. 8, a cladding layer 56 then may be formed withintrench 52 using any suitable deposition process such as PVD, IBD, ALD,electroplating or electroless plating. Cladding layer 56 may be formedof all of the materials and layers that comprise cladding layer 30 asdescribed with reference to FIG. 3.

In an alternative embodiment of the invention, referring momentarily toFIG. 17, an insulator barrier layer 66 may be formed within trench 52before the deposition of cladding layer 56. Insulator barrier layer 66may be used to reduce or eliminate detrimental interaction between asubsequently formed top cladding layer, as described below, and claddinglayers 20. Insulator barrier layer 66 may be formed of any suitable lowtemperature material, including any of those materials that may be usedto form first and second material layers 24, 50. Preferably, insulatorbarrier layer 66 is formed of PEN.

Referring to FIG. 9, a buffer material layer 58 then may be formedwithin trench 52 and overlying cladding layer 56. Buffer material layer58 may be formed of any of the materials that comprise buffer materiallayer 38 as described with reference to FIG. 4.

As illustrated in FIG. 10, any excess portion of cladding layer 56 andbuffer material layer 58 then may be removed by any suitableplanarization process known in the semiconductor industry, such as, forexample, chemical mechanical planarization or electrochemical mechanicalplanarization, or any other suitable removal process, such as etching.Once a suitable portion of cladding layer 56 and buffer material layer58 has been removed, a portion of cladding layer 30 remains to form atop cladding layer 60 over bit line 10. Again, depending on the amountof planarization performed, top cladding layer 60 may or may not besubstantially planar. Accordingly, as will be appreciated, a fluxconcentrating system 62 comprising top cladding layer 60 may be formedusing the above-described exemplary embodiment of the present invention.In addition to top cladding layer 60, flux concentrating system 62 mayalso comprise cladding layers 20 of bit line 10.

FIGS. 11-15 illustrate yet a further exemplary embodiment of the presentinvention. Elements of FIGS. 11-15 that have the same reference numbersas FIGS. 1-10 are the same corresponding FIGS. 1-10 elements. The methodmay begin by providing bit line 10 that is formed within insulativematerial substrate 12. First material layer 24 is formed overlying bitline 10 and substrate 12 and a second material layer 50 is formedoverlying first material layer 24.

Referring to FIG. 12, a portion of second material layer 50 and firstmaterial layer 24 may be removed by patterning and etching usingconventional techniques to form a trench 70 within second material layer50 and first material layer 24. It will be appreciated that trench 70should be at least as wide as bit line 10 so that the subsequentlydeposited cladding layer, as described in detail below, may focus themagnetic flux of bit line 10 to an underlying magnetoelectronics element(not shown). Second material layer 50 is preferably etched by a dry etchin plasma, as is well known in the semiconductor industry. In oneembodiment of the invention, second material layer 50 may be etched suchthat etching is stopped by first material layer 24, which as previouslydescribed is formed as either a layer of material that is not amenableto the dry etching process, or which indicates a change of material thatstops the etching due to an endpoint detection signal. In anotherembodiment of the invention, an etch of second material layer 50 isperformed, followed by a subsequent overetch of first material layer 24,which overetch does not result in exposure of bit line 10. Firstmaterial layer 24 then is etched with a wet etch chemistry that etchesfirst material layer 24 significantly faster than second material layer50. First material layer 24 is etched until bit line 10 is exposed andis overetched until trench 70 includes an undercut 72 of first materiallayer 24. In this exemplary embodiment, overetching is conducted toproduce a sufficient undercut 72 so that, upon subsequent deposition ofa cladding layer, as discussed below, a discontinuous cladding layer isachieved.

As illustrated in FIG. 13, a cladding layer 74 then may be formed withintrench 70 using a deposition process such as PVD, IBD, ALD orelectroless plating. Cladding layer 74 may be formed of all of thematerials and layers that comprise cladding layer 30 as described withreference to FIG. 3. As described above, due at least in part to thesubstantial undercut 72 of first material layer 24, cladding layer 74preferably is discontinuous, forming a top cladding layer 76 overlyingbit line 10 and an ancillary cladding layer 78 overlying second materiallayer 50.

Referring to FIG. 14, a buffer material layer 80 than may be formedwithin trench 70 and overlying top cladding layer 76 and ancillarycladding layer 78. Buffer material layer 80 may be formed of any of thematerials that comprise buffer material layer 38 as described withreference to FIG. 4.

As illustrated in FIG. 15, second material layer 50 and ancillarycladding layer 78 then may be removed by any suitable planarizationprocess known in the semiconductor industry, such as, for example,chemical mechanical planarization, electrochemical mechanicalplanarization, and the like. Accordingly, a flux concentrating system 82that includes top cladding layer 76 is formed overlying bit line 10.Flux concentrating system 82 may also comprise cladding layers 20 of bitline 10.

FIG. 16 illustrates an enlarged perspective view of a portion of arandom access memory device 90 formed in accordance with anotherexemplary embodiment of the present invention. Elements of FIG. 16 thathave the same reference numbers as FIG. 1-10 are the same as thecorresponding FIG. 10 elements. Random access memory device 90 includesa plurality of magnetic memory units 92. Magnetic memory units 92 may begiant magnetoresistance (GMR) elements or magnetic tunnel junction (MTJ)elements. Magnetic memory units 92 may be formed on or within anysuitable semiconductor substrate 94, which may include any suitablesemiconductor devices (not shown), such as for example, transistors,data lines, input/output circuits, data/address decoders, and the like.

Each of magnetic memory units 92 is magnetically coupled to a bit line10 such that a magnetic field created by bit line 10 may be used toprogram the plurality of magnetic memory units 92. The magnetic fieldcreated by bit line 10 may be focused toward the memory units 92 by aflux concentrating system 96. In one exemplary embodiment, asillustrated in FIG. 16, flux concentrating system 96 includes claddinglayers 20 and top cladding layer 60. It will be appreciated, however,that flux concentrating system 96 may comprise any of the otherexemplary embodiments of a top cladding layer described herein and mayinclude only a top cladding layer.

Thus it is apparent that there has been provided, in accordance with theinvention, a method for fabricating a flux concentrating system for usein a magnetoelectronics device. Although various embodiments of theinvention have been described and illustrated with reference to specificembodiments thereof, it is not intended that the invention be limited tosuch illustrative embodiments. For example, it will be appreciated that,while the above-described embodiments of the method of the presentinvention comprise forming two layers overlying the bit line, the methodalso may include forming a single layer overlying the bit line, etchingthe single layer to form a trench and depositing a cladding layer in thetrench. A buffer material layer may then be formed within the trench andoverlying the cladding layer and any excess portion of the claddinglayer and buffer material layer then may be removed as described above.This exemplary embodiment of the invention may result in a fluxconcentrating system similar to that illustrated in FIG. 10.Correspondingly, the method of the present invention may compriseforming three or more layers overlying the bit line. Additionally, thecladding layer is not limited to one flux concentrating layer but mayinclude additional flux concentrating layers. Moreover, the claddinglayer may include barrier layers in addition to the first and secondbarrier layers. Those of skill in the art will recognize that manyvariations and modifications of such embodiments are possible withoutdeparting from the spirit of the invention. Accordingly, it is intendedto encompass within the invention all such modifications and variationsas fall within the scope of the appended claims.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any element(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeatures or elements of any or all the claims. As used herein, the terms“comprises,” “comprising,” or any other variation thereof, are intendedto cover a non-exclusive inclusion, such that a process, method,article, or apparatus that comprises a list of elements does not includeonly those elements but may include other elements not expressly listedor inherent to such process, method, article, or apparatus.

1-19. (canceled)
 20. A method for fabricating a flux concentratingsystem for use in a magnetoelectronics device, the method comprising thesteps of: providing a bit line formed in a substrate; forming a firstmaterial layer overlying said bit line and said substrate; forming asecond material layer overlying said first material layer; etching saidsecond material layer with a dry plasma etch to form a trench; etchingsaid first material layer using a wet etch chemistry that causes saidfirst material layer to etch significantly faster than said secondmaterial layer; depositing a cladding layer in said trench; forming abuffer material layer overlying said cladding layer; and removing aportion of said buffer material layer and a portion of said claddinglayer.
 21. The method of claim 20, wherein the step of forming saidfirst material layer comprises forming said first material layer ofplasma-enhanced nitride and the step of forming said second materiallayer comprises forming said second material layer from tetraethylorthosilicate.
 22. The method of claim 20, the step of depositing acladding layer comprising depositing a flux concentrating layer that isan electrically conducting magnetic material having sufficiently highpermeability to concentrate magnetic flux to a desired area.
 23. Themethod of claim 20, the step of depositing a cladding layer comprisingdepositing a flux concentrating layer formed of nickel iron (NiFe). 24.The method of claim 20, further comprising the step of forming aninsulator barrier layer in said trench before the step of depositing acladding layer.
 25. The method of claim 20, wherein the step of etchingsaid first material layer results in exposing at least a portion of asurface of said bit line and wherein said method further comprises thestep of pre-deposition sputter etching said surface of said bit line.26. The method of claim 20, wherein the step of removing a portion ofsaid buffer material layer and a portion of said cladding layer furthercomprises removing said second material layer.
 27. A method offabricating a flux concentrating system for use in a magnetoelectronicsdevice, the method comprising the steps of: providing a bit line formedin a substrate; forming a first material layer overlying said bit lineand said substrate; forming a second material layer overlying said firstmaterial layer; etching said second material layer with a dry plasmaetch to form a trench; etching said first material layer using a wetetch chemistry that causes said first material layer to etchsignificantly faster than said second material layer and that effects anoveretching of said first material layer so that said trench comprisesan undercut of said first material layer relative to said secondmaterial; depositing a cladding layer within said trench, said claddinglayer comprising a first portion overlying said bit line and a secondportion overlying said second material layer; forming a buffer materiallayer within said trench, said buffer material layer overlying at leastsaid first portion of said cladding layer; and removing said secondportion of said cladding layer and a portion of said buffer materiallayer.
 28. The method of claim 27, wherein the step of forming saidfirst material layer comprises forming said first material layer ofplasma-enhanced nitride and the step of forming said second materiallayer comprises forming said second material layer from tetraethylorthosilicate.
 29. The method of claim 27, the step of depositing acladding layer comprising depositing a flux concentrating layer that isan electrically conducting magnetic material having sufficiently highpermeability to concentrate magnetic flux to a desired area.
 30. Themethod of claim 29, the step of depositing a cladding layer comprisingdepositing a flux concentrating layer formed of nickel iron (NiFe). 31.The method of claim 27, wherein the step of etching said first materiallayer results in exposing at least a portion of a surface of said bitline and wherein said method further comprises the step ofpre-deposition sputter etching said surface of said bit line.
 32. Themethod of claim 27, wherein said first portion and said second portionof said cladding layer are continuous.
 33. The method of claim 27,wherein said first portion and said second portion of said claddinglayer are discontinuous.
 34. The method of claim 32, the step ofremoving said second portion of said cladding layer and a portion ofsaid buffer material layer further comprising removing said secondmaterial layer.
 35. The method of claim 33, the step of removing saidsecond portion of said cladding layer and a portion of said buffermaterial layer further comprising removing said second material layer.